1. Field of the Invention
The present invention relates to an image processing technique to process image data to be printed out by a printer.
2. Description of the Related Art
There have been increasing social demands for documents, which require high security, to identify a leaking source when a leakage occurs. According to a method to identify a leakage source, a marking indicating identification such as information regarding a person who output a document may be given to the document. In order to satisfy such a demand, for example, Japanese Laid-Open Patent Application No. 2006-237858 suggests a marking technique to extract information embedded in a document when scanning the document, the information being embedded in the document when printing the document.
According to the marking technique, the information is embedded in the document by applying a certain process to the document image to be printed. There may be no problem if the document image is processed because a change in a document image caused by such a process to embed special information does not affect the contents of the document. However, the meaning of a document containing a drawing or the like may be changed if the drawing is changed to some extent. That is, when embedding information in a document containing a drawing or the like, it is necessary to maintain geometrical features of the drawing or the like.
There is suggested a conventional technique to apply a deformation process or an intensity process to an image after rendering. However, such a technique is not usable because the deformation of image may destroy a geometrical feature of a drawing or the like. Additionally, because a drawing or the like is expressed by a binary image in many cases, it may be difficult to embed information in the drawing by using intensity of the drawing.
Also, there is suggested a technique to embed information in a document by changing intervals of characters or lines contained in a drawing. However, if the characters themselves are a part of a total design, the total design is changed by the change in the intervals of characters or lines. Thus, this technique is not suitable. This technique also has an additional problem in that it takes a long time to perform the process of embedding information because there must be a process of extracting characters by analyzing the image of the drawing.